Smelting of zinciferous materials



Aug. 23, 1938. H, NAJARIAN 2,127,633

SMELTING OF ZI NCIFEROUS MATERIALS Filed May 8, 1955 Patented Aug. 23,1938 UNITED STATES SMELTING OF ZINCIFEROUS Herand K. Najarian, Beaver,Pa., assignor to St. Joseph Lead Company, New York, N. Y., a corporationof New York Application May 8, 1935, Serial No. 20,507

9 Claims.

ducing agents, together with any desired modi-- fying agents, may bebrought into a condition 1 for eflicient smelting and the valuescontained therein economically separated.

The invention comprises forming zinciferous materials and carbonaceousmaterials into concretionary aggregates by contacting solid nuclearparticles with finely divided zinciferous and carbonaceous materialswhile subjecting the nuclear particles to continuous rolling andsubjecting the concretionary aggregates to a smelting temperature.

A preferred method of making the concretionary aggregates is describedin application Serial No. 20,505 filed May 8, 1935, and suitableapparatus 'formaking the concretions is described in application SerialNo. 20,506, filed May 8, 1935.

The invention will be described for the purpose of illustration withreference to the accompanying drawing showing a flow sheet of oneembodiment of the method of the invention.

In the drawing, l is a ball mill wherein zinciferous materials, such ascalcined zincsulphide ore, are ground together with a reducing fuel,such as coke, and fluxes or other desired modifying agents, preferably,to a fineness of about- 200 mesh U. S. standard screen. The groundmaterials are conveyed by belt conveyor 2 to screw conveyor 3 whichcarries the materials into rtary drum 4. Nucleus material, for example,

lumps of coke about to inch in size, is fed through nozzles 8.

By the action of the alternate spraying with binder liquid and coatingwith the finely divided ore and coke, and the continuous rolling in drum4, the ore and coke are built up into a shell around the nuclei, asdescribed more fully in the applications above referred to, formingconcretions of, for example, 1 to 1% inches in diameter.

A typical concretion is shown in Fig. 2, where- ,in I represents thenucleus, for example, of coke,

and 2 represents the shell of zinciferous and carboniferous material.

The formed concretions are then passed 5 through drying chamber ill bymeans of conveyor 9 and thence preferably into preheater I I wherein theconcretions may advantageously be heated to nearly the reduction point,for example, 600 to 700 C., by any suitable heating means. By 10 thisoperation the volatile content of the binder used, or of thecarbonaceous material, is driven off.

The preheated concretions are then fed into a furnace l2 which may beail-externally heated retort, a blast furnace, an electric arc furnace,or an electric resistance furnace. The furnace shown inthe drawing byway of example is an electric resistance furnace of the type describedin U. S. Patent 1,7 75,591 to Gaskill.

When the concretions have reached smelting temperature in the furnace,zinc vapor is freely and evenly evolved and may be condensed to metalliczinc in condenser l3, or oxidized to zinc oxide at M.

The residues may be discharged from the retort or furnace by anyconvenient means, as, for example, rotating table IS. The residues maythen be separated and any substantial values therein returned to theprocess.

The following are several examples of formulas for zinciferousconcretions, which are illustrative of the wide variety of zinciferousmaterials which may be utilized in the invention:

Example No. 1

Compo- I Material smon Weight Perce'n Pounds 99% l00M. Zn 69. 900

see

Zn Fe Coke, ground with ore (reclaim) 91% 200 M. l00

Cokenuclel +a s" -5/s" Example No. 2

Material Composition Weight 7 Percent Pounds Droes Zn 65.00 120 Othermetals 27. 00

Drop ZnO Zn 72.00 317 Other metals 21.00

Magnetic zinc residue Zn 27. 20 413 Bio; 25. 40 Fe 18. 70 O 7. 20

Coke ground with ore 150 Binter nuclei Zn 59. 210

Suiphite liquor, 10 RmmA 185 Example N0. 3

Material Composition Weight Percent Pounds Drop zinc oxide Zn 72.00 260.Other metals 21.00 C 2. 00

Magnetic zinc residue Zn 27. 20 615 Other metals 4. 00 S10: 23. 40 Fe18. 70 C 7. 20

Reclaim coke ground with ore Zn 7. 00

Lime rock ground with ore .4 30

Coke nuclei; Fe 3. 00 70 Sulphite liquor, 10 Baum The above Exampes 1-3are useful in the manufacture of lead-free zinc oxides, zinc metals, andother zinc products.

Examples 4, 5 and 6 are used in the manufacture of leaded zinc oxide andrelatively high lead zinc metal.

Example No. 4

Composi- Material on Weight Percent Pounds Flue dust Zn 54. 00 890 Pb15. 10 Fe 7. 00 S 1. 10

Reclaimed coke Zn 1. 00 110 Coke nuclei 70 Sulphite liquor, 10 Baum 185Example N0. 5

Material Composition Weight Percent Pou'mix Flue dust Zn 54. 390

Pb 15. 10 Fe 7.00 s 1.10

Reclaimed coke Zn 7. on

Sinter nuclei Zn 59. 80 210 Metallica 9. 40 Si0 8.80 Fe 7.90 S 10Sulphlte liquor, 10 Baume 185 Example No. 6

Material Composition Weight Percent Pounds Flue dust Zn 54. 00 1000 Pb15. 10 Fe 7. 00 B l. 10

Sinter nuclei Z11 59.80 210 Metallics 9. 40 SiO; 8.80 Fe 7.90 10Bulphite liquor, 10 Baum 165 and temperature necessary to completereduction are materially reduced. For example, in the or- Y dinaryBelgian type zinc retort, reduction of the zinc-bearing concretion willbe complete in from 6 to 8 hours at a temperature of 1200 0., contrastedwith a time of from 16 to 18 hours when smelting the ordinary loosecharge which is commonly used.

Furthermore, due to the intimate mixture of the carbonaceous andzincifero'us materials, the temperature at which reduction reactionshave comparable efliciencies would be 975 C. for the 'concretions and1225 C. for the loose charges of ordinary practice. This is due to thefact that in the reduction of an aggregate, such as 'a lump of ore,sinter, or an agglomerate of ore alone, the reduction progresses fromthe outside surface inwardly, the difliculties of bringing about contactwith the carbonaceous material, or of effecting carbonaceous gaspenetration being greatly increased. as the size of the particleincreases, inasmuch as the inert materials carried by the ore when it isin the form of lumps or agglomerates having appreciable size, serve tosegregate as reduction proceeds on the surface of the particles,preventing free carbon contact and making the penetration of thecarbonaceous gases diflicult. Therefore, the time and temperaturerequired for the final efflcient reduction of such ores is greatlyincreased over that required by the finely ground .metalliierousmaterials intimately mixed with finely ground carbonaceous materials inthe concretions of this invention.

With a carbonaceous nucleus, considerable vapor pressure at thetemperature of I reduction must be exerted from that direction andreduction proceeds rapidly, inasmuch as the novel conditions ofstructure of the concretion promote th realization of nearly idealreduction.

The concretions being spherical, or nearly so, in form, the spacebetween the bodies for the circulation of the gases and vapors is at amaximum, thus resulting in a very rapid heat transfer from one part ofthe retort to the other and the assurance, due to the open charge, thatlocal pressures will not be built up, which seriously impair smeltlugemciency. Inasmuch as, referring particularly to zinciferous ores, thepreferable carbonaceous content. is metallurgical coke containingrelatively low sulphur and very low residual volatile content, theconcretions of the invention may be used in the direct production of themetallic oxides from the volatile metals, and a high grade productobtained, which cannotbe realized, particularly in the manufacture ofzinc oxides or the basic lead sulphates by the fuming process, when theraw zinciferous or plumbiferous materials are briquetted with the cokingbituminous coals. Inasmuch as the limitations placed upon the cokingprocess by the reduction temperature of these metalliferous materialsare such that the volatile content of the briquette or agglomeratecannot be reduced below about 2%, the result is that as this material issubsequently reduced in the smelting furnace, the remaining volatilehydrocarbon of the briquette or agglomerate is distilled off in thereduction process and carried out with the gases and vapors, excessivelydiscoloring the oxides produced by these processes and making them unfitfor commercial use in many of the arts. Furthermore, a briquette madewithout the aid of the flowing or coking coals, or an excessive amountof tar or pitch, has not proved satisfactory in shaft furnaces, duelargely to the fact that, although great pressures are used by thenumerous briquette pressing devices, the moisture content at the time ofpressing must be kept relatively low, with the result that the particlesare not thoroughly wetted, that the binder and the matrix formed by thesubsequent reaction due to heat or chemical reaction are poorlydistributed, and that when the briquette is highly heated it sandsrapidly, causing a loss of furnace porosity and a consequent loss ofsmelting efficiency due to the difliculties of obtaining uniform heatpenetration to all parts of the charge.-

In blast furnace smelting, if the charge consists or concretionaryagglomerates, made by using the fuel portion of the charge in the formof lumps of coke, coal, or charcoal as nuclei, and coating them with thefinely ground mixture of ores, fluxes, flue dust and the like, improvedoperation and reduction in fuel consumption are obtained due to the factthat the concretions permit free and more uniform circulation ofreducing gases in the furnace while the coating on the fuel inhibits thedissolution of the carbon in the fuel at the upper zones of the blastfurnace by ascending carbonic acid gas.

The solid nucleus of the concretion of this invention-whatever it may becomposed ofgreatly reinforces the structure and prevents breakage andcrumbling.

I claim:

1. A method of smelting zinciferous materials which comprises formingconcretions of finely divided zinciferous material and carboniferousmaterial about solid nuclei of a material entering into the smeltingreaction and subjecting the concretions to smelting temperature. I

2. A method of smelting zinciferous materials which comprises formingconcretionsof finely divided zinciferous material and carboniferousmaterial about solid nuclei of reducing fuel and subjecting theconcretions to smelting temperature.

3. A method of smelting zinciferous materials which comprises formingconcretions of finely divided zinciferous material and carboniferous material about solid nuclei of coke and subjecting the concretions tosmelting temperature.

4. A method of smelting zinciferous materials which comprises formingconcretions of finely divided zinciferous material and carboniferousmaterial about solid nuclei of sintered zinciferous material andsubjecting the concretions to smelting temperature.

5. A method of smelting zinciferous materials which comprises formingconcretions of finely divided zinciferous material and carboniferousmaterial about solid nuclei of a material entering into the smeltingreaction, preheating the concretions to below smelting temperature, andsubjecting the preheated concretions to smelting temperature.

6. A method of smelting zinciferous materials which comprises formingconcretions of finely divided zinciferous material and carboniferousmaterial about solid nuclei of a material entering into the smeltingreaction and subjecting the concretions to smelting temperature bypassing an electric current through a column of the concretions.

7. A method of smelting zinciferous materials which comprises formingconcretions of finely divided zinciferous material and carboniferousmaterial about solid nuclei of a material entering into the smeltingreaction, preheating the concretions to below smelting temperature, andsubjecting the preheated concretions to smelting temperature by passingan electric current through a column of the concretions.

8. A method of smelting zinciferous materials which comprises contactingsolid particles of a material entering into the smelting reaction withfinely divided zinciferous material and carboniferous material and witha binder material while subjecting the particles to continuous rollinguntil a shell of desired size has "uilt up about the solid particles,thereafter continuing the rollinging until a shell of desired size hasbuilt up about the solid particles, thereafter continuing the rollingoperation until the substance of said shell is well plasticized,indurating the concretions thus formed by heating and subjecting theinduratedconcretions to smelting temperature.

K. NAJARIAN.

